1. Field of the Invention
The present invention relates to a microstructural body made from a wafer by a semiconductor process, such as micro electro mechanical systems (MEMS), a microstructural body array formed by a plurality of microstructural bodies, and a production method therefor. Here, the term “microstructural body” mainly refers to a structural body that has a minute size of the order of micrometers and that includes a movable portion. For example, the microstructural body can be used in a dynamic quantity sensor (e.g., an acceleration sensor, a pressure sensor, or a gyro sensor), a light deflector, an optical switch, and an optical modulation element.
2. Description of the Related Art
U.S. Patent Application Publication Nos. 2008/100898 A1 and 2009/067033 A1 disclose micro electro mechanical systems (MEMS) used as an actuator and a sensor. For example, a movable portion is provided on a substrate so that the movable portion and the substrate constitute a capacitor having variable electrostatic capacitance. This capacitor can be used as an electrostatic actuator or a sensor for detecting the change in capacitance. Alternatively, a microstructural body is integrated on a substrate including an integrated circuit. Such a microstructural body is used, for example, as a light deflector for deflecting light. Further, a plurality of microstructural bodies are arranged to form an array. In particular, a MEMS device in which a microstructural body including a movable portion with a reflecting surface deflects light in a two-dimensional manner can be used as an optical switch or a spatial intensity or phase modulator.
In a microstructural body of the related art including a movable portion, the spring constant of a torsion spring is changed by the difference in temperature between the microstructural body and a substrate on which the microstructural body is formed and the elongation of the substrate. This makes displacement motion of the movable portion unstable. Further, in a microstructural body including a movable portion capable of two-dimensional torsional displacement, if the spring constants in two torsional displacement directions are decreased, the spring constants in other directions also decrease. Consequently, unnecessary displacement is likely to occur with torsional displacement.